Gluing is used particularly for joining parts of non-weldable materials, such as reinforced termoset polymer material, for example pipes and pipe parts of fibre-reinforced polymers, FRP.
In patent publication NO 311272 a glued joint and a joining method are is described. More specifically, a joint is formed by gluing together two objects of which at least one comprises a pipe formed joining section that can be thread or brought over the other object, distinguished in that a delimited void is formed between the object and the pipe formed joining section of the first object, and that a first bore extends from the external face of the pipe formed joining section to said void, through which first void glue can be pressed into the void. Said publication further contains description on forming a joint in agreement with the above, by gluing together two objects, of which at least one are pipe shaped or pipe formed in the area at the joining section and arranged to be thread over the other object by use of said section, distinguished by closing an opening formed between the pipe formed joining section and the other object when the pipe formed section is brought over said object, to create a delimited void or space between the objects, and by pressing glue through a first bore formed in the pipe formed joining section in the purpose of filling the void with glue.
The glue joint of NO 311272 has proved to very successful, and it finds use particularly in pipe systems of relatively moderate dimensions, such as pneumatic systems, sprinkler systems, cooling systems, systems for mild chemicals, draining, waste and cleaning. For such pipe systems the labour of installation amounts to about 80% of the costs, while the component costs only amounts to about 20%. It has turned out that pipe systems with glued joints according to NO 311272 can cut the costs of installation in half, because the installation is substantially simplified. The pipes that are used are particularly made of glass fibre and vinyl ester, the coupling parts are typically made of phenol resins and glass fibre, while the glue typically is of the epoxy type, for example a type of Araldite.
However, one embodiment of the glued joint of NO 311272 requires particular attention to ensure the aimed quality. Said embodiment is illustrated on FIG. 3 (corresponds to FIG. 2 of NO 311272), comprising two venting or relieving bores or holes 14, of which one venting bore is near the inner side of the void and one venting bore is near the outer side of the void. With an inner side it is here meant further into the joint, which means the side of the void closest to the end of the male part 9. By installation a glue gun is brought towards the bore 13, glue is injected into the void 10 and filling it completely, after which the glue by further injection will leak out of the venting holes 14. It has turned out that by installation it must particularly be observed that glue seeps out to substantial extent from both venting holes, and in particular the inner venting hole. If glue is not filled up well also to the inner venting hole, there can be a possible leakage way for fluid within the pipe system with glued joints in agreement with FIG. 2 of the patent publication NO 311272. This is because fluid under pressure in the pipe system will follow the interface between the pipe parts 9 and 8, and if the fluid has sufficient pressure it can extend through the seal 11 and reach the inner venting hole 14. On FIG. 3 the leakage way is indicated with an arrow L. There is a demand for a coupling which is completely safe with respect to the above mentioned problem, and the objective of the present invention is to provide such a coupling.